This application is related to Japanese Patent Applications No. 2000-310869 filed on Oct. 11, 2000, and No. 2001-226223 filed on Jul. 26, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a heat storage tank which stores a cooling liquid of a liquid-cooled engine. For example, the heat storage tank is suitably used for a vehicle having a water-cooled engine.
2. Description of Related Art
In a conventional heat storage tank described in JP-A-10-77839, the flow of cooling water is controlled by an electric valve. Because the electric valve is used for controlling the flow of cooling water in the heat storage tank, the number of components is increased, a structure of the heat storage tank becomes complex, and the production cost of the heat storage tank is increased.
In view of the foregoing-problems, it is an object of the present invention to provide a heat storage tank which is manufactured with a reduced cost.
According to the present invention, in a heat storage tank for storing a cooling liquid of a liquid-cooled engine, a fluid passage communicating with an interior of a tank body is provided. A valve body for opening and closing the fluid passage is constructed to open the fluid passage when a dynamic pressure applied to the valve body by the cooling liquid is larger than a predetermined pressure, and to close the fluid passage when the dynamic pressure applied to the valve body by the cooling liquid is smaller than the predetermined pressure. Accordingly, the flow passage can be accurately opened and closed without using an electric valve. Therefore, the heat-storage tank can be manufactured with a reduced cost.
Preferably, the valve body is constructed to close the fluid passage by a density difference between the cooling liquid and the valve body when the dynamic pressure applied to the valve body is smaller than the predetermined pressure. Alternatively, the valve body is constructed to close the fluid passage by a pressure due to the weight of the valve body and the weight of the cooling liquid when the dynamic pressure applied to the valve body is smaller than the predetermined pressure. Therefore, the structure of the valve body can be made simpler in the heat storage tank.
The cooling liquid circuit includes a first liquid circuit having at least a radiator for cooling the cooling liquid, and a second liquid circuit including the heat storage tank. A pump is disposed in the second liquid circuit so that cooling liquid circulates between the second liquid circuit and the liquid-cooled engine independently from the first liquid circuit. Therefore, high-temperature cooling liquid stored in the heat storage tank can be directly supplied to the engine without being affected by operation of the first liquid circuit. Thus, heating operation of the engine can be effectively facilitated.